> though diesel engines spit out a bunch of bad stuff.

Exactly. The noxious tailpipe emissions in a city are usually from diesel trucks, small vehicles like motorcycles (small or absent catalytic converters), modified vehicles (catalytic converter removed or diesel reprogrammed to smoke), but not modern gasoline ICE vehicles.

The love for diesel engines in many European countries was always confusing to me.

PM2.5 is also a broad category of particulates that come from many sources. The PM2.5 levels in the air depend on many sources, with wind being a major factor in changing PM2.5 levels. It’s hard to draw conclusions when a number depends on the weather and a lot of other inputs.

Diesel looks good if you are focusing primarily on fuel economy (mpg / L/100km), and when companies cheat the tests on other emissions:

https://en.wikipedia.org/wiki/Volkswagen_emissions_scandal

When you remove the cheating and give adequate weight to those emissions, diesel for passenger vehicles makes a lot less sense.

Modern diesel engines with DPF and DEF are pretty clean from a particulate and NOx standpoint. Of course there are still older diesels on the road, mainly buses and trucks. In the USA, diesel is so unpopular as a passenger car engine that it's not even worth worrying about.

> The love for diesel engines in many European countries was always confusing to me.

That's a thing of the past as as early as in 2023 diesels were already a smaller percentage of new cars than non-hybrid EVs:

https://www.acea.auto/figure/fuel-types-of-new-passenger-car...

To add to what others said: diesels always had a reputation of reliability. The cast-iron TDI 1.9 is legendary but even Italian cars fitted with the JTD line would just work and not require maintenance. I recall making light of a friend who was driving an Alfa Romeo until he mentioned that actually it's been more reliable than anything else he's driven - at least in terms of powertrain issues.

The love for diesel came from a catastrophic misunderstanding and the resulting belief that CO2 must be reduced at all costs. Diesel engines of the past produced slightly less CO2 per km than petrol engines in exchange for much worse overall emissions. The fact that they were slightly more efficient in terms of fuel consumption helped with the sales pitch, too.

> The love for diesel engines in many European countries was always confusing to me.

And turns out the whole thing was a lie. https://en.wikipedia.org/wiki/Diesel_emissions_scandal

It's unfortunate that so much rhetoric around environmentalism is based on faulty claims. It's starting to make me sceptical of environmental claims in general.

The latest one is AI data center water use- the extreme numbers like 5 liters of water per ChatGPT image just makes me feel sad that we can't have a civil discussion based on the facts. Everything is so polarized.

>The love for diesel engines in many European countries was always confusing to me.

It's expressly incentivized by their tax system.

Imagine the year is 1988 and you're some snooty jerk in Europe about to buy a Mercedes. Why on earth would you go with the noisy, smelly diesel option if not to save A TON of money over the life of the vehicle?

When I was at the military they told us that in case of war the government would start appropriating diesel cars, since those are compatible with the fuel the military uses and that there were ancient incentives to buy this type of car to make sure there were enough of them.

Diesel was promoted in the UK when we were worried about CO2 emissions. There was a subsequent back-pedal when particulates became a prominent issue

I believe the popularity of diesel car in Europe is actually a tax-related hack.

The idea is that diesel is the "work" fuel, for shipping, construction, etc... While gasoline is the "consumer" fuel, for personal use, motorsports, etc... Make the former expensive and it will affect the entire economy, everything will become more expensive and less competitive. Making gasoline more expensive will not have the same impact.

So, put high taxes on gasoline. The result was an increase in popularity of diesel cars, that cost less to run because of taxes.

Now, the situation is changing. Diesel, at least the one that is legal to use on the road is taxed at a level closer to gasoline. Diesel cars are also becoming less and less welcome with regards to low emission zones and green taxes, so many people are going back to gasoline.